Catheters of the prior art included the use of symmetrically disposed balloons in which—after deployment and inflation—the drainage ports of each inflated catheter are always located well above the upper reach of the inflated balloon (normalized to gravity), viz., high in the user's bladder above the entry port of the latter. Result: large amounts of the user's urine remain in the bladder, especially if the bladder sags or tilts toward the entry port, due to fatigue, aging or the like (hereinafter called “residual urine stowage”).